Abstract The proposal outlines an integrated research and career development plan for Yun Fang, Ph.D to complete postdoctoral training in the laboratory of Dr. Peter Davies and transition to an independent academic position by establishing a multi-disciplinary research program in cardiovascular pathophysiology. The PI is currently an American Heart Association Fellow who is trained in the fields of molecular biology, bioengineering, and vascular biology. During the 2 year mentored period, the PI will receive additional academic guidance from the mentor and the advisory committee at the University of Pennsylvania. The career development plan is designed to equip the PI with necessary knowledge and skills in biomedical research for a successful transition as an independent academician, leading to a RO1 as the R00 phase of the work progresses. The overall research goal is to determine the role of microRNA-10a (miR-10a) in mediating endothelial phenotypes in relation to the initiation and development of atherosclerosis. MicroRNA-mediated post-transcriptional regulation is poorly understood in arterial biology and pathology. Preliminary studies conducted by the K99 PI demonstrate that differential topographic expression of miR-10a in distinct arterial sites significantly contributes to the endothelial heterogeneity associated with susceptibility to atherosclerosis. Notably, endothelial miR-10a is significantly suppressed in vivo in athero-susceptible regions exposed to disturbed blood flow in a large animal model. Further functional genomics and biochemical analyses demonstrated that miR-10a promotes the athero-protective phenotype in endothelial cells by suppressing NF-B-mediated inflammation (PNAS in press). The research proposal tests the overall hypothesis that flow and/or hypercholesterolemia-sensitive miR-10a dynamically modulates endothelial phenotypes in the initiation and progression of atherosclerosis. Aim 1 will test the hypothesis that athero-protective miR-10a suppresses endothelial inflammation and Endoplasmic Reticulum stress (ER stress) by direct inhibition of a cohort of positive NF-B and Unfolded Protein Response (UPR) responsive molecules. Aim 2 will test the hypothesis that athero- relevant hemodynamic force regulates mechano-sensitive transcription factors, leading to differential control of endothelial miR-10a biogenesis at athero-susceptible and athero-protected regions in vivo. And Aim 3 will develop a transgenic mouse model that exhibits inducible expression of endothelial miR-10a to demonstrate the causality of endothelial miR-10a expression and atherosclerosis, thereby testing in vivo the hypothesis that athero-protective miR-10a inhibits endothelial inflammation and ER stress, alleviating atherosclerotic burden. The goal will be achieved by integrating system biology and molecular analysis in both in vitro and in vivo systems, leading to mechanistic understandings of the down-stream gene networks and up-stream regulators of endothelial miR-10a with respect to atherosclerosis.